At right is a photo that shows more of the brewery at my last session.
Below is another shot from its construction in 2005 (click it for maxi-view). It's a photo from before the copper plumbing was built on, with the pipes drawn on in Photoshop. I had previously sketched it out legal pads, newspaper proofs at work, etc., and this was the final scheme before I went out and bought the pipes and valves and tubing. The blue lines are plastic tubing, the brown are copper and the brass ball valves are green. Pump's that orange thing at the bottom. Note that the mash tun is my backup one. It's nice (and I got it free!) but the blue one is bigger and that's what I've been using:
Also note the changes that happened during construction. The vertical pipe up to the mash tun has a more elegant, diagonal rise to it, and the orientation of the pump was changed when I realized that the planned position would create an air bubble around the impeller with no way to bleed it off (why the heck isn't this &*%#! thing working?).
I also added foam insulation around the pipes, although I think more of that will be needed for winter brewing in Virginia. I'm losing heat through that plastic tube going into the tun in particular.
You'll see the diagram also has a "heating coil," like in a heat-exchanged recirculating mash system (HERMS). This is not very effective as a way to drastically change the temperature of the mash, but it definitely has benefits. It doesn't make step-mashing a breeze (I don't really do this anyway), but it does allow some temperature control of the wort while it recirculates, and recirculation is really the beauty of this system.
When you recirculate, you are constantly running the wort through the grainbed as long as the pump is on. This turns the grainbed into a very solidly bedded filter, which results in incredibly clear wort as well as a very good mash yield. You never have to stir anything, either. In fact you shouldn't.
After an hour of mashing, or close to it, I turn on the pump and begin moving wort out of the bottom of the tun, through the pump and back up to the top of the tun where it can pass through the grain again. To keep the flow into the tun from disrupting the grainbed (that pump can push pretty hard), there is a "fountain" system at the top of the tun to slow down the flow and kind of lay it gently on top of the grain. Here's a picture of the open tun lid during a mash, and you can sort of see how the fountain works:
During recirculation, if I want, I can turn two valves and shunt the wort through the heating coil, a length of 3/8 copper pipe that's immersed in the hot water tank. If the tank is full of hot water, this of course heats the wort. On warm days, this is a good way to boost the temp of the mash and stop the conversion process, also called "mashing out." On cold days it's not so effective for that.
I run the pump until the wort is clear enough for me to clearly see my finger through the clear plastic tubing coming out of the tun. You can see this tube above. Magical! You know that tan rubbery stuff that's left in the bottom of your kettle after you boil? Well, this makes it a thing of the past. Recirculating leaves almost all of that crud in the mash tun. (The iodine is for testing the wort for conversion, which I rarely do anymore.)
This next picture is a better illustration of how clear your wort can get, although this is in fact wort that has been boiled and is headed for the chiller:
To finish for today, here is a shot of what happens to the spent grain when the wort has been drawn off into the kettle and is boiling. My son and I detached the tun and lugged it down to the compost pile, and dumped a nice, warm layer of goodness on the heap. It will be great for next year's vegetables:
If you're disposing of spent grain for the first time, especially in warm weather, dump it AWAY from the house. After about 48 hours it is squirming with worms and STINKS like few other things you have experienced. This is also a good reason to thoroughly clean your tun as soon as it's empty, and not put it off:
Until next time ...
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